1. Field of the Invention
The present invention relates to a shift register, and more particularly, to a shift register which is capable of simultaneously supplying all-drive signals to gate lines for an all-drive period and sequentially supplying scan pulses to the gate lines forwardly or reversely for a scan period.
2. Discussion of the Related Art
In general, a liquid crystal display device is adapted to display an image by adjusting light transmittance of a liquid crystal using an electric field. To this end, the liquid crystal display device includes a liquid crystal panel having pixel areas arranged in matrix form, and a driving circuit for driving the liquid crystal panel.
In the liquid crystal panel, a plurality of gate lines and a plurality of data lines are arranged to intersect each other, and pixel areas are located respectively in areas defined by the intersections of the gate lines and the data lines. A pixel electrode and a common electrode for application of an electric field to each of the pixel areas are formed in the liquid crystal panel.
Each pixel electrode is connected to a corresponding one of the data lines via the source terminal and drain terminal of a thin film transistor (TFT), which is a switching device. The TFT is turned on by a scan pulse applied to the gate terminal thereof via a corresponding one of the gate lines to charge a data signal from the corresponding data line in the pixel electrode.
The driving circuit includes a gate driver for driving the gate lines, a data driver for driving the data lines, a timing controller for supplying control signals for control of the gate driver and data driver, and a power supply for supplying various driving voltages to be used in the liquid crystal display device.
The gate driver includes a shift register for sequentially supplying scan pulses to the gate lines to sequentially drive pixels in the liquid crystal panel on a line-by-line basis.
On the other hand, when the liquid crystal display device is driven, it is common that the gate lines are driven in order. However, in some cases, it may be necessary to simultaneously drive the gate lines or change the driving direction of the gate lines. A conventional shift register has a disadvantage in that it cannot attain such driving.